The Nanoscale in Chemical Reaction Engineering: From Analysis to Design

Spectroscopy and microscopy, combined with quantum chemical and statistical mechanical calculations, provide increasingly detailed insights into active sites, catalytic mechanisms and kinetics. Many catalysts are nanoporous materials, or employ a nanoporous support, with a network of broader meso- and macropores to reduce diffusion limitations and mitigate effects of catalyst deactivation.

Novel synthesis methods increasingly enable us to realize hierarchically structured porous catalysts or supports with controlled pore sizes, topology and morphology at multiple length scales, as well as supported catalytic species of a controlled structure (varying from nanoparticles to enzymes and metal-organic complexes with tuned chemical structures). A chemist’s dream is to control both the chemical and the geometrical architecture of catalysts with atomic resolution. However, from a chemical engineering point of view, it is especially valuable to learn which structural features matter most and are robust enough to be applied in a scalable manner within the constraints of an industrial chemical reactor.

Besides innovation at the atomistic scale (e.g., the composition of nanoparticle clusters or new microporous catalytic frameworks), there are nanoscale effects that can be engineered to achieve higher catalytic performance. We discuss a few, focusing on nano-confinement effects in supported enzyme and metal-organic catalysis; surface roughness; and the effects of grain boundaries in zeolite catalysis.